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| United States Patent |
5,660,086
|
|
Carey
|
August 26, 1997
|
Connecting rod
Abstract
A connecting-rod has the axes (16) of the cap screws, or bolts, (4)
inclined to each other. The big end housing (3,2) is of reduced width and
has protruding bearing shells (11). The stem has a cross section of
minimum perimeter in the central portion.
| Inventors:
|
Carey; Charles (Via Castellani 31, 10060 Campiglione (TO), IT)
|
| Appl. No.:
|
558706 |
| Filed:
|
November 16, 1995 |
Foreign Application Priority Data
| Current U.S. Class: |
74/579E; 29/888.09; 74/579R; 123/90.61; 403/344 |
| Intern'l Class: |
G05G 001/00 |
| Field of Search: |
74/579 R,579 E
123/90.61
29/888.09
403/344
|
References Cited
U.S. Patent Documents
| 3889553 | Jun., 1975 | Ballheimer | 74/579.
|
| 4827795 | May., 1989 | Machida et al. | 74/579.
|
| 4856366 | Aug., 1989 | Nikolaus | 74/579.
|
| 5109605 | May., 1992 | Hoag et al. | 29/888.
|
| Foreign Patent Documents |
| 746785 | Jun., 1933 | FR | 74/579.
|
| 1067388 | Jun., 1954 | FR | 74/579.
|
| 1001544 | Jan., 1957 | DE | 74/579.
|
| 1210263 | Feb., 1966 | DE | 74/579.
|
| 875417 | Aug., 1961 | GB | 74/579.
|
| 898268 | Jun., 1962 | GB | 74/579.
|
| 981446 | Jan., 1965 | GB | 74/579.
|
| 1369948 | Oct., 1974 | GB | 74/579.
|
Primary Examiner: Luong; Vinh T.
Attorney, Agent or Firm: Larson & Taylor
Claims
I claim:
1. A connecting-rod assembly comprising an arcuate connecting-rod cap, a
main body having a relatively small connecting rod eye at one end thereof
and an opposite end having an arcuate shape, and elongate fasteners for
attaching said cap to said opposite end of said main body so as to define
a big end opening having a central axis, said fasteners being received in
holes in bore walls defining said big end opening, said fasteners having a
thread diameter and having longitudinal axes which are angled so as to
approach one another in the direction of the small connecting-rod eye, the
spacing of the longitudinal axes of said fasteners from the closest
adjacent surface of the big end opening being less than 85% of the thread
diameter of the fastener, said holes having an entrance surface and the
length of said fasteners along the longitudinal axes between the entrance
surface of said holes and a plane perpendicular to the longitudinal axis
of the main body and passing through the central axis of the big end
opening being less one and a quarter times said thread diameter, and said
bore walls including ribs formed therein adjacent to said holes.
2. A connecting-rod assembly according to claim 1, wherein said length is
less than said thread diameter.
3. A connecting-rod assembly according to claim 2, wherein said length is
less than three quarters of said thread diameter.
4. A connecting-rod assembly according to claim 3, said opposite end of
said main body and said arcuate cap are of single piece construction and
solely define said big end opening, and said opposite end and said cap are
joined together along a mating surfaces which define a plurality of
contact planes of different angles with respect to the longitudinal axes
of the respective fasteners.
5. A connecting rod assembly according to claim 1 further comprising at
least one arcuate shell bearing fitted in said big end opening.
6. A connecting rod assembly according to claim 5 wherein said shell
bearing is flush with said big end opening.
7. A connecting rod assembly according to claim 5 wherein an edge of said
shell bearing extends outwardly beyond said big end opening in the
direction of the central axis thereof.
8. A connecting rod assembly according to claim 7 wherein said shell
bearing extends around at least 40% of the circumference of said big-end
opening.
9. A connecting-rod assembly comprising ah arcuate connecting-rod cap, a
main body having a stem interconnecting a small connecting rod eye at one
end thereof and an arcuate shaped opposite end, and elongate fasteners for
attaching said cap to said opposite end of said main body so as to define
a big end connecting-rod eye having a central axis, said fasteners being
received in holes in bore walls defining said big end connecting-rod eye,
said fasteners having a thread diameter and having longitudinal axes which
are angled so as to approach one another in the direction of the small
connecting-rod eye, said stem including ribs and having a cross-section
transverse to the plane of the rod of a smaller perimeter in a central
portion of the stem than that of a portion of the stem adjacent to each of
said connecting-rod eyes such that a portion of the stem in the plane
containing the axes of said connecting-rod eyes is thicker in the central
portion of the stem and diminishes in directions towards both of said
connecting-rod eyes, and such that the ribs of a substantial portion of
the stem are located near and extend substantially parallel to the
projected axes of the fasteners.
10. A connecting-rod according to claim 9, wherein the ribs converge and
diverge along the length of the stem.
11. A connecting-rod assembly comprising an arcuate connecting-rod cap, a
main body having a stem interconnecting small eye connecting rod eye at
one end thereof and an arcuate shaped opposite end, and elongate fasteners
for attaching said cap to said opposite end of said main body so as to
define a big end connecting-rod eye having a central axis, and at least
one arcuate shell bearing fitted in said big end connecting-rod eye and
having an edge and a radial thickness, the length of the bore walls of the
big end connecting-rod eye, in the direction of the axis of the big end
connecting-rod eye, being such that the edge of the arcuate shell bearing
extends beyond the bore walls for at least 40% of the circumference of the
bore walls, and said bore walls including raised pads for guidance of the
connecting-rod in the direction of the axis of the big end connecting-rod
eye.
Description
FIELD OF THE INVENTION
This invention relates to a connecting-rod, in particular a connecting-rod
for internal-combustion piston engines.
BACKGROUND OF THE INVENTION
A known connecting-rod comprises a main body and a cap both being held
together with bolts or screws and forming an opening in which are fitted
bearing shells and in which pass a crankpin. The joining surfaces between
the main body and cap are either machined or fractured and lie in planes
substantially perpendicular to the axis of the bolt or screw which passes
through the respective surface. The main body comprises a stem which
connects an opening at one end, the small connecting-rod eye, to part of
an opening at the other end, the big end, the remaining part of this
opening being formed in the cap, and this stem has ribs, either joined
with a web or otherwise, which connect the two openings. The bearing
shells are held in the opening by means of a radial pressure due to an
interference between the outer surface of the bearing shell and the inner
surface of the opening, the inner surface of the opening extending in a
direction parallel to the crankpin axis over a greater amount than the
bearing shells.
SUMMARY OF THE INVENTION
This invention seeks to lighten the connecting-rod particularly in the
region of the opening formed by the main body and cap by inclining the
axes of the bolts or screws to reduce the length of each bolt or screw and
their surrounding housing and to result in a more favorable stress
distribution between the bolt and ribs in the stem of the main body
particularly with regard to the bending stresses in the bolt, and also to
reduce the width of the opening in the direction of the crankpin axis such
that a substantial amount of the bearing shells inserted in the opening
remain nearly flush, flush or proud of the opening and with one or more
raised portions that serve to guide the connecting rod between the
crankpin side faces on the crankshaft. The connecting-rod is preferably
made of two pieces, a cap and main body joined together with preferably
two screws or bolts. The main body and cap are preferably constructed of a
substantially metal material, cast, forged or sintered.
According to a first aspect of the present invention there is provided a
connecting-rod which has the bolts or screws that attach the connecting
rod cap to the main body of the connecting-rod to have their extended
longitudinal mid-axes so as to approach one another in the direction of
the small connecting-rod eye, preferably passing inside this opening, and
to have the stem of the main body so formed that the projected axes of the
bolts or screws pass along, near, or parallel to the ribs in the stem for
a substantial part of their length preferably each rib having its outside
surface to lie less than one nominal thread diameter of the screw or bolt,
or more preferably less than three quarters, or even more preferably one
half the said diameter from the projected axis of said screw or bolt for a
distance of at least half the length of the stem as measured along the
connecting-rod axis, from the end which is connected to the big end
opening, the said length of stem being defined as the minimum distance
along the connecting-rod axis between the vertex of the big end opening
bore surface and the vertex of the little eye bore surface, and for the
same outer surface of each rib to not cross the projected axis of the
screw and bolt which lies on the same side of the connecting-rod axis as
said rib such that it is greater than one half the nominal thread diameter
distant from the said axis, this condition to be met over a distance of at
least half the stem length as measured along the connecting-rod axis. In
addition the inclination of the bolt or screw axis to the axis passing
through the centers of each opening permits the shortening of the bolt or
screw, particularly that part which passes through the cap such that the
length of the screw shank along its mid-axis between the underhead or not
and a plane passing perpendicular to the connecting-rod axis and
containing the axis of the cylindrical big end opening where all or the
greater part of the said screw head or nut lies on the cap side of this
plane, is less than one and a quarter or preferably one or even more
preferably three quarter diameters of the nominal screw thread diameter
while having the axis of the screw to pass a minimum distance equal or
less than 85% of the screw or bolt thread diameter from the bore surface
of the big end opening. To maintain sufficient strength and rigidity in
the cap it is preferred to make provision for side ribs which partly or
fully enclose each screw head or nut, said ribs preferably having a height
measured perpendicular to the cap surface that abuts the screw underhead
or not in a plane that lies parallel to the screw axis a distance of one
half the nominal thread diameter from this axis in a direction towards the
big end opening bore said plane being also perpendicular to the plane
containing the screw axes, of at least one nominal thread diameter. If the
inclination of the axis of the screw to the axis passing between both
openings in the connecting-rod is small then lateral movement of the cap
can be resisted by frictional forces between the two surfaces in addition
to any cap location provided by dowel pins or the screws themselves,
however if the inclination is great, typically more than ten degrees, the
lateral forces may be large and fracture split main body and cap will be
preferable in resisting lateral movement between the contacting surfaces
due to the multitude of interlocking surfaces in the fracture plane. This
method also avoids expensive machining of the joint faces between the main
body and cap even when such faces are preferably machined to be a plane
surface without steps or serrations. The joining plane of each screw or
bolt, as defined as the plane lying on average equidistant from joint
surfaces either side of this plane, should preferably lie within twenty
degrees or even more preferably five degrees of perpendicularity to the
said screw or bolt axis.
A second aspect of the invention provides the stem connecting the small
connecting-rod eye opening to the big end opening to have a cross-section
transverse to the plane of the rod having a smaller perimeter in a central
portion of the stem than in a portion near each connecting-rod eye
opening, resulting in a section in the plane containing the two
connecting-rod eye axes which is thicker in the central portion of the
stem diminishing in the direction of both connecting-rod eye openings,
thickness being taken in a direction parallel to the connecting-rod eye
axes. A central portion of the stem is defined as that which is greater
than one quarter of the distance between connecting-rod eye axes from oft
connecting-rod eye axes. Such an arrangement allows the force flux in the
lower part of one rib to be transferred to the upper part of the opposite
rib without excessive bending stresses in each rib and thereby improving
the force distribution between the little eye housing and the inclined
bolt or screw, having their projected axes to pass preferably within two
nominal thread diameters from the outer surface of the rib that lies on
the opposite side of the connecting-rod axis from the screw whose axis is
being projected, for a distance of at least one quarter the stem length as
measured along the connecting-rod axis.
A third aspect of the invention provides that the length of the bore walls
of the big end opening, in the direction of the axis of the big end
opening, are such that the edge of the arcuate shell bearing or bearings
that are fitted inside the big end opening and which have a radial
thickness which is typically less than 5% of the diameter of the big end
opening, remain less than 60% of the radial nominal thickness of the
bearing from the edge, or preferably flush, or more preferably extend
beyond the bore walls for a substantial part of their circumference
preferably at least 40% of the circumference. In this way the bearing
shell outer surface may be free from contact and unsupported by the
connecting-rod big end opening over part of its load carrying portion thus
relying on the strength of its own shell, which is typically made from
steel with a bearing overlay, to resist the bearing loads between the
crankpin, bearing shell, and intermediate oil film. Such bearing shells
being typically produced in two halves each half fitting into the main
body housing and cap housing respectively, their arcuate from consisting
of one outer surface which contacts the respective housing bore walls
having an interference between these surfaces to ensure their location and
utilizing small tangs to locate their position in the axial direction of
the housing bore, each tang fitting into a corresponding slot in the cap
and main housing bore walls. In addition should the connecting-rod be
guided in the axial direction of the crankpin by contact, intermittent or
otherwise, with radial surfaces on the crankshaft, then one or more raised
surfaces can be provided on the sides of the connecting-rod such that they
prevent contact between the bearing shell and the radial surfaces on the
crankshaft, thereby providing the necessary axial guidance. The raised
pads can also conveniently coincide with the ribs on the cap which enclose
the screw heads. In the case of two or more connecting-rods being mounted
on the same crankpin then raised pads can be arranged to come into contact
with each other on respectively adjacent connecting-rods.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention are illustrated diagrammatically in the
drawings in which;
FIG. 1 shows a side view of a connecting-rod.
FIG. 2 shows a longitudinal section of a connecting-rod together with the
big end connecting-rod eye shell bearings, taken generally along line
15--15 of FIG. 1.
FIGS. 3,4,5 show stem sections, taken generally along line 19--19, 20--20,
and 21--21, respectively.
FIG. 6 shows an alternative stem cross section to that of FIG. 4.
FIG. 7 is a fragmentary side elevational view of an alternative embodiment
of the stem.
FIG. 8 is a section taken generally along line 19--19 of FIG. 7.
FIG. 9 is a fragmentary side elevational view of yet another embodiment of
the stem.
FIG. 10 is a section taken generally along line 19--19 of FIG. 9.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the drawing, the connecting-rod comprises a main body 1 which
has a small connecting-rod eye 5 and a part of a large connecting-rod eye,
the big end, 3 which is completed by a cap 2. The cap 2 is attached to the
main body 1 by means of elongate fasteners such as screws 4, as shown, or
bolts with nuts (not shown), whose extended longitudinal mid-axes 16
approach one another in the direction of the small connecting-rod eye and
which pass near and parallel to a rib for a substantial portion of the
length of the stem. The holes 6, in which pass the screws, may be closed
or part closed at one end. The mating surfaces 14 between the main body 1
and cap 2 may be machined or preferably fractured and may have the
direction of their planes of contact at various angles to the mid-axis of
each screw. Although not shown the heads of the screws or nuts on the
bolts may be sufficiently sunk in the cap between the ribs 12, such that
the length of the screw shank along its axis 16 between the underhead
surface or nut surface that abuts the cap and the plane perpendicular to
the axis 15 and in which lies the axis 17 may be less than one and a
quarter or more preferably one or even more preferably three quarter
nominal thread diameters of the screw or bolt, while having the axis of
the screw 16 passing less than or equal to 85% of the thread diameter from
the bore surface of the big end opening.
An arcuate shell bearing or bearings 11 is held within the large
connecting-rod eye by means of the cap 2 and housing 3 in the main body 1.
The lateral length of the bore walls of the big end opening O, the
direction of the axis 17 of the big end opening, is such that the edges of
the arcuate bearing shells, having typically a radial thickness less than
5% of the diameter of the big end opening 23 (also referred to as the big
end connecting-rod eye), remain less than 60% from the edge, or preferably
flush or more preferably extend beyond the bore walls for a substantial
part of their circumference, preferably more than 40% of the
circumference. Where the axial guidance of the connecting-rod in the
direction of the longitudinal axis 17 of the big end opening 23 is
controlled by contact, intermittent or otherwise, with the crank shaft, a
laterally extending boss or bosses 12 of the large connecting-rod eye
housing are provided as shown in FIG. 1 and FIG. 2 and these may
conveniently coincide with the ribs enclosing the screw head or nuts on
the cap as shown.
Also shown in FIG. 1 are two ribs 7 which comprises a part of the stem of
the main body and whose outer sides adjoin the outer contours of the big
end and who converge upon each other at some point between the
connecting-rod eyes and then diverge as ribs 8 to adjoin the small
connecting rod eye, thereby having a section 15 in the plane containing
the two axes 17 and 18 as shown in FIG. 2 where a thick central portion of
the stem 9 diminishes to a thinner part 10 in each direction towards both
connecting-rod eye housings 3 and 5. FIG. 3 shows the section 19 in the
central portion of the stem having a shorter perimeter than in sections 20
and 21 nearer each connecting-rod eye as shown in FIG. 4 and FIG. 5
respectively. Thus the projected axes of the screws 16 are seen to pass
near and almost parallel to the ribs 7 and 8 for a substantial part of the
length of the stem.
FIG. 6 shows an alternative to sections 20 and/or 21 where the stem is
comprised of two struts without a connecting central portion 10.
FIGS. 7 and 8 show another embodiment of the central portion of the stem
where the side ribs 7 and 8 of the stem remain defined but a substantially
thick portion 9 remains between them.
FIGS. 9 and 10 show another embodiment of the stem where an outer fin or
fins 13 exist over part or all of the converging, diverging ribs 7 and 8.
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